The invention relates to a process for the production of a planar conductor path system for integrated semiconductor circuits.
By a photo-lithographic etching technique, conductor paths are produced on a semiconductor surface. This leads to considerable profiling of the semiconductor surface. A passivation layer applied upon the latter, and which can consist, for example, of sputtered SiO.sub.2, frequently only insufficiently covers the edges of the etched portions and then is unable to fulfill the desired function. Thus, for example, the passivation layer is not sufficiently flat for a second metallization layer to be applied subsequently.
In order to avoid a heavy profiling of the metallization plane, it is known, instead to remove the unrequired metal to convert these zones into non-conductive regions.
Thus, for example, in H. Tsanemitsu and H. Shiba, NEC Research and Development, 25, p. 74-80 (1972), the aluminum is converted as follows: First, the aluminum is applied to the whole of the surface of the semiconductor arrangement. The geometry of the conductor paths is subsequently covered with thin but densely pored oxide in a photolithographic process. When the photo lacquer required for the photolithographic process has been removed, the exposed aluminum which is not required is entirely converted into porous oxide in another anodization process. Here the first, dense oxide serves as protective mask for the underlying metal. The metal paths are thus separated from one another by the porous oxide.
The same process for aluminum layers to which silicon or copper is added as an alloy component is known. It is necessary to modify the process as with aluminum-copper and aluminum-silicon alloys for it is not readily possible to form pore-free forming oxide.
A fundamental disadvantage of these processes lies in the fact that the thick, porous oxide is produced electrochemically. This requires on the one hand additional conductor paths solely for this process, and on the other hand the current supply through the metal layer which is to be converted at the end of the process is not guaranteed. This results in the fact that residues of metal remain on the base - that is, the surface on which the aluminum or Al alloy is applied to the base - of the oxidized zones. They are joined on the underside to the base, for example, to insulating SiO.sub.2. The newly formed oxide, however, separates them from the current conducting layer which is becoming increasingly thinner. Thus, a reliable and complete conversion of the zones between the conductor paths is possible only at random. This fault can lead to short-circuits during operation.